Adware
Alternatively referred to as malware, sneakware, or spyware, adware is a program installed without a user's consent or knowledge during the install of another program. Much like spyware, adware tracks individuals Internet activities and habits to help companies advertise more efficiently.
Adware is usually installed on a computer with free programs since the developers are often paid if they include it with their program. Like spyware, adware can be located and removed from a computer using software utilities available on the Internet.
Also see: Security definitions, Software, Spyware